12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
27 #include "gc/shenandoah/shenandoahConcurrentGC.hpp"
28 #include "gc/shenandoah/shenandoahControlThread.hpp"
29 #include "gc/shenandoah/shenandoahDegeneratedGC.hpp"
30 #include "gc/shenandoah/shenandoahFreeSet.hpp"
31 #include "gc/shenandoah/shenandoahFullGC.hpp"
32 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
33 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
34 #include "gc/shenandoah/shenandoahMark.inline.hpp"
35 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
36 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
37 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
38 #include "gc/shenandoah/shenandoahUtils.hpp"
39 #include "gc/shenandoah/shenandoahVMOperations.hpp"
40 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
41 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
42 #include "memory/iterator.hpp"
43 #include "memory/metaspaceUtils.hpp"
44 #include "memory/metaspaceStats.hpp"
45 #include "memory/universe.hpp"
46 #include "runtime/atomic.hpp"
47
48 ShenandoahControlThread::ShenandoahControlThread() :
49 ConcurrentGCThread(),
50 _alloc_failure_waiters_lock(Mutex::leaf, "ShenandoahAllocFailureGC_lock", Monitor::_safepoint_check_always, true),
51 _gc_waiters_lock(Mutex::leaf, "ShenandoahRequestedGC_lock", Monitor::_safepoint_check_always, true),
52 _periodic_task(this),
53 _requested_gc_cause(GCCause::_no_cause_specified),
54 _degen_point(ShenandoahGC::_degenerated_outside_cycle),
55 _allocs_seen(0) {
56
57 reset_gc_id();
58 create_and_start();
59 _periodic_task.enroll();
60 if (ShenandoahPacing) {
61 _periodic_pacer_notify_task.enroll();
62 }
63 }
64
65 ShenandoahControlThread::~ShenandoahControlThread() {
66 // This is here so that super is called.
67 }
68
69 void ShenandoahPeriodicTask::task() {
70 _thread->handle_force_counters_update();
71 _thread->handle_counters_update();
72 }
73
74 void ShenandoahPeriodicPacerNotify::task() {
75 assert(ShenandoahPacing, "Should not be here otherwise");
76 ShenandoahHeap::heap()->pacer()->notify_waiters();
77 }
78
79 void ShenandoahControlThread::run_service() {
80 ShenandoahHeap* heap = ShenandoahHeap::heap();
81
82 GCMode default_mode = concurrent_normal;
83 GCCause::Cause default_cause = GCCause::_shenandoah_concurrent_gc;
84 int sleep = ShenandoahControlIntervalMin;
85
86 double last_shrink_time = os::elapsedTime();
87 double last_sleep_adjust_time = os::elapsedTime();
88
89 // Shrink period avoids constantly polling regions for shrinking.
90 // Having a period 10x lower than the delay would mean we hit the
91 // shrinking with lag of less than 1/10-th of true delay.
92 // ShenandoahUncommitDelay is in msecs, but shrink_period is in seconds.
93 double shrink_period = (double)ShenandoahUncommitDelay / 1000 / 10;
94
95 ShenandoahCollectorPolicy* policy = heap->shenandoah_policy();
96 ShenandoahHeuristics* heuristics = heap->heuristics();
97 while (!in_graceful_shutdown() && !should_terminate()) {
98 // Figure out if we have pending requests.
99 bool alloc_failure_pending = _alloc_failure_gc.is_set();
100 bool explicit_gc_requested = _gc_requested.is_set() && is_explicit_gc(_requested_gc_cause);
101 bool implicit_gc_requested = _gc_requested.is_set() && !is_explicit_gc(_requested_gc_cause);
102
103 // This control loop iteration have seen this much allocations.
104 size_t allocs_seen = Atomic::xchg(&_allocs_seen, (size_t)0, memory_order_relaxed);
105
106 // Check if we have seen a new target for soft max heap size.
107 bool soft_max_changed = check_soft_max_changed();
108
109 // Choose which GC mode to run in. The block below should select a single mode.
110 GCMode mode = none;
111 GCCause::Cause cause = GCCause::_last_gc_cause;
112 ShenandoahGC::ShenandoahDegenPoint degen_point = ShenandoahGC::_degenerated_unset;
113
114 if (alloc_failure_pending) {
115 // Allocation failure takes precedence: we have to deal with it first thing
116 log_info(gc)("Trigger: Handle Allocation Failure");
117
118 cause = GCCause::_allocation_failure;
119
120 // Consume the degen point, and seed it with default value
121 degen_point = _degen_point;
122 _degen_point = ShenandoahGC::_degenerated_outside_cycle;
123
124 if (ShenandoahDegeneratedGC && heuristics->should_degenerate_cycle()) {
125 heuristics->record_allocation_failure_gc();
126 policy->record_alloc_failure_to_degenerated(degen_point);
127 mode = stw_degenerated;
128 } else {
129 heuristics->record_allocation_failure_gc();
130 policy->record_alloc_failure_to_full();
131 mode = stw_full;
132 }
133
134 } else if (explicit_gc_requested) {
135 cause = _requested_gc_cause;
136 log_info(gc)("Trigger: Explicit GC request (%s)", GCCause::to_string(cause));
137
138 heuristics->record_requested_gc();
139
140 if (ExplicitGCInvokesConcurrent) {
141 policy->record_explicit_to_concurrent();
142 mode = default_mode;
143 // Unload and clean up everything
144 heap->set_unload_classes(heuristics->can_unload_classes());
145 } else {
146 policy->record_explicit_to_full();
147 mode = stw_full;
148 }
149 } else if (implicit_gc_requested) {
150 cause = _requested_gc_cause;
151 log_info(gc)("Trigger: Implicit GC request (%s)", GCCause::to_string(cause));
152
153 heuristics->record_requested_gc();
154
155 if (ShenandoahImplicitGCInvokesConcurrent) {
156 policy->record_implicit_to_concurrent();
157 mode = default_mode;
158
159 // Unload and clean up everything
160 heap->set_unload_classes(heuristics->can_unload_classes());
161 } else {
162 policy->record_implicit_to_full();
163 mode = stw_full;
164 }
165 } else {
166 // Potential normal cycle: ask heuristics if it wants to act
167 if (heuristics->should_start_gc()) {
168 mode = default_mode;
169 cause = default_cause;
170 }
171
172 // Ask policy if this cycle wants to process references or unload classes
173 heap->set_unload_classes(heuristics->should_unload_classes());
174 }
175
176 // Blow all soft references on this cycle, if handling allocation failure,
177 // either implicit or explicit GC request, or we are requested to do so unconditionally.
178 if (alloc_failure_pending || implicit_gc_requested || explicit_gc_requested || ShenandoahAlwaysClearSoftRefs) {
179 heap->soft_ref_policy()->set_should_clear_all_soft_refs(true);
180 }
181
182 bool gc_requested = (mode != none);
183 assert (!gc_requested || cause != GCCause::_last_gc_cause, "GC cause should be set");
184
185 if (gc_requested) {
186 // GC is starting, bump the internal ID
187 update_gc_id();
188
189 heap->reset_bytes_allocated_since_gc_start();
190
191 MetaspaceCombinedStats meta_sizes = MetaspaceUtils::get_combined_statistics();
192
193 // If GC was requested, we are sampling the counters even without actual triggers
194 // from allocation machinery. This captures GC phases more accurately.
195 set_forced_counters_update(true);
196
197 // If GC was requested, we better dump freeset data for performance debugging
198 {
199 ShenandoahHeapLocker locker(heap->lock());
200 heap->free_set()->log_status();
201 }
202
203 switch (mode) {
204 case concurrent_normal:
205 service_concurrent_normal_cycle(cause);
206 break;
207 case stw_degenerated:
208 service_stw_degenerated_cycle(cause, degen_point);
209 break;
210 case stw_full:
211 service_stw_full_cycle(cause);
212 break;
213 default:
214 ShouldNotReachHere();
215 }
216
217 // If this was the requested GC cycle, notify waiters about it
218 if (explicit_gc_requested || implicit_gc_requested) {
219 notify_gc_waiters();
220 }
221
222 // If this was the allocation failure GC cycle, notify waiters about it
223 if (alloc_failure_pending) {
224 notify_alloc_failure_waiters();
225 }
226
227 // Report current free set state at the end of cycle, whether
228 // it is a normal completion, or the abort.
229 {
230 ShenandoahHeapLocker locker(heap->lock());
231 heap->free_set()->log_status();
232
233 // Notify Universe about new heap usage. This has implications for
234 // global soft refs policy, and we better report it every time heap
235 // usage goes down.
236 Universe::heap()->update_capacity_and_used_at_gc();
237
238 // Signal that we have completed a visit to all live objects.
239 Universe::heap()->record_whole_heap_examined_timestamp();
240 }
241
242 // Disable forced counters update, and update counters one more time
243 // to capture the state at the end of GC session.
244 handle_force_counters_update();
245 set_forced_counters_update(false);
246
247 // Retract forceful part of soft refs policy
248 heap->soft_ref_policy()->set_should_clear_all_soft_refs(false);
249
250 // Clear metaspace oom flag, if current cycle unloaded classes
251 if (heap->unload_classes()) {
252 heuristics->clear_metaspace_oom();
253 }
254
255 // Commit worker statistics to cycle data
256 heap->phase_timings()->flush_par_workers_to_cycle();
257 if (ShenandoahPacing) {
258 heap->pacer()->flush_stats_to_cycle();
259 }
260
261 // Print GC stats for current cycle
262 {
263 LogTarget(Info, gc, stats) lt;
264 if (lt.is_enabled()) {
265 ResourceMark rm;
266 LogStream ls(lt);
267 heap->phase_timings()->print_cycle_on(&ls);
268 if (ShenandoahPacing) {
269 heap->pacer()->print_cycle_on(&ls);
270 }
271 }
272 }
291 double current = os::elapsedTime();
292
293 if (ShenandoahUncommit && (explicit_gc_requested || soft_max_changed || (current - last_shrink_time > shrink_period))) {
294 // Explicit GC tries to uncommit everything down to min capacity.
295 // Soft max change tries to uncommit everything down to target capacity.
296 // Periodic uncommit tries to uncommit suitable regions down to min capacity.
297
298 double shrink_before = (explicit_gc_requested || soft_max_changed) ?
299 current :
300 current - (ShenandoahUncommitDelay / 1000.0);
301
302 size_t shrink_until = soft_max_changed ?
303 heap->soft_max_capacity() :
304 heap->min_capacity();
305
306 service_uncommit(shrink_before, shrink_until);
307 heap->phase_timings()->flush_cycle_to_global();
308 last_shrink_time = current;
309 }
310
311 // Wait before performing the next action. If allocation happened during this wait,
312 // we exit sooner, to let heuristics re-evaluate new conditions. If we are at idle,
313 // back off exponentially.
314 if (_heap_changed.try_unset()) {
315 sleep = ShenandoahControlIntervalMin;
316 } else if ((current - last_sleep_adjust_time) * 1000 > ShenandoahControlIntervalAdjustPeriod){
317 sleep = MIN2<int>(ShenandoahControlIntervalMax, MAX2(1, sleep * 2));
318 last_sleep_adjust_time = current;
319 }
320 os::naked_short_sleep(sleep);
321 }
322
323 // Wait for the actual stop(), can't leave run_service() earlier.
324 while (!should_terminate()) {
325 os::naked_short_sleep(ShenandoahControlIntervalMin);
326 }
327 }
328
329 bool ShenandoahControlThread::check_soft_max_changed() const {
330 ShenandoahHeap* heap = ShenandoahHeap::heap();
331 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
332 size_t old_soft_max = heap->soft_max_capacity();
333 if (new_soft_max != old_soft_max) {
334 new_soft_max = MAX2(heap->min_capacity(), new_soft_max);
335 new_soft_max = MIN2(heap->max_capacity(), new_soft_max);
336 if (new_soft_max != old_soft_max) {
337 log_info(gc)("Soft Max Heap Size: " SIZE_FORMAT "%s -> " SIZE_FORMAT "%s",
338 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
339 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
340 );
341 heap->set_soft_max_capacity(new_soft_max);
342 return true;
343 }
344 }
345 return false;
346 }
347
348 void ShenandoahControlThread::service_concurrent_normal_cycle(GCCause::Cause cause) {
349 // Normal cycle goes via all concurrent phases. If allocation failure (af) happens during
350 // any of the concurrent phases, it first degrades to Degenerated GC and completes GC there.
351 // If second allocation failure happens during Degenerated GC cycle (for example, when GC
352 // tries to evac something and no memory is available), cycle degrades to Full GC.
353 //
354 // There are also a shortcut through the normal cycle: immediate garbage shortcut, when
355 // heuristics says there are no regions to compact, and all the collection comes from immediately
356 // reclaimable regions.
357 //
358 // ................................................................................................
359 //
360 // (immediate garbage shortcut) Concurrent GC
361 // /-------------------------------------------\
362 // | |
363 // | |
364 // | |
365 // | v
366 // [START] ----> Conc Mark ----o----> Conc Evac --o--> Conc Update-Refs ---o----> [END]
367 // | | | ^
368 // | (af) | (af) | (af) |
369 // ..................|....................|.................|..............|.......................
370 // | | | |
371 // | | | | Degenerated GC
372 // v v v |
373 // STW Mark ----------> STW Evac ----> STW Update-Refs ----->o
374 // | | | ^
375 // | (af) | (af) | (af) |
376 // ..................|....................|.................|..............|.......................
377 // | | | |
378 // | v | | Full GC
379 // \------------------->o<----------------/ |
380 // | |
381 // v |
382 // Full GC --------------------------/
383 //
384 ShenandoahHeap* heap = ShenandoahHeap::heap();
385 if (check_cancellation_or_degen(ShenandoahGC::_degenerated_outside_cycle)) return;
386
387 GCIdMark gc_id_mark;
388 ShenandoahGCSession session(cause);
389
390 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
391
392 ShenandoahConcurrentGC gc;
393 if (gc.collect(cause)) {
394 // Cycle is complete
395 heap->heuristics()->record_success_concurrent();
396 heap->shenandoah_policy()->record_success_concurrent();
397 } else {
398 assert(heap->cancelled_gc(), "Must have been cancelled");
399 check_cancellation_or_degen(gc.degen_point());
400 }
401 }
402
403 bool ShenandoahControlThread::check_cancellation_or_degen(ShenandoahGC::ShenandoahDegenPoint point) {
404 ShenandoahHeap* heap = ShenandoahHeap::heap();
405 if (heap->cancelled_gc()) {
406 assert (is_alloc_failure_gc() || in_graceful_shutdown(), "Cancel GC either for alloc failure GC, or gracefully exiting");
407 if (!in_graceful_shutdown()) {
408 assert (_degen_point == ShenandoahGC::_degenerated_outside_cycle,
409 "Should not be set yet: %s", ShenandoahGC::degen_point_to_string(_degen_point));
410 _degen_point = point;
411 }
412 return true;
413 }
414 return false;
415 }
416
417 void ShenandoahControlThread::stop_service() {
418 // Nothing to do here.
419 }
420
421 void ShenandoahControlThread::service_stw_full_cycle(GCCause::Cause cause) {
422 GCIdMark gc_id_mark;
423 ShenandoahGCSession session(cause);
424
425 ShenandoahFullGC gc;
426 gc.collect(cause);
427
428 ShenandoahHeap* const heap = ShenandoahHeap::heap();
429 heap->heuristics()->record_success_full();
430 heap->shenandoah_policy()->record_success_full();
431 }
432
433 void ShenandoahControlThread::service_stw_degenerated_cycle(GCCause::Cause cause, ShenandoahGC::ShenandoahDegenPoint point) {
434 assert (point != ShenandoahGC::_degenerated_unset, "Degenerated point should be set");
435
436 GCIdMark gc_id_mark;
437 ShenandoahGCSession session(cause);
438
439 ShenandoahDegenGC gc(point);
440 gc.collect(cause);
441
442 ShenandoahHeap* const heap = ShenandoahHeap::heap();
443 heap->heuristics()->record_success_degenerated();
444 heap->shenandoah_policy()->record_success_degenerated();
445 }
446
447 void ShenandoahControlThread::service_uncommit(double shrink_before, size_t shrink_until) {
448 ShenandoahHeap* heap = ShenandoahHeap::heap();
449
450 // Determine if there is work to do. This avoids taking heap lock if there is
451 // no work available, avoids spamming logs with superfluous logging messages,
452 // and minimises the amount of work while locks are taken.
453
454 if (heap->committed() <= shrink_until) return;
455
456 bool has_work = false;
457 for (size_t i = 0; i < heap->num_regions(); i++) {
458 ShenandoahHeapRegion *r = heap->get_region(i);
459 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
460 has_work = true;
461 break;
462 }
463 }
464
465 if (has_work) {
466 heap->entry_uncommit(shrink_before, shrink_until);
467 }
468 }
469
470 bool ShenandoahControlThread::is_explicit_gc(GCCause::Cause cause) const {
471 return GCCause::is_user_requested_gc(cause) ||
472 GCCause::is_serviceability_requested_gc(cause);
473 }
474
475 void ShenandoahControlThread::request_gc(GCCause::Cause cause) {
476 assert(GCCause::is_user_requested_gc(cause) ||
477 GCCause::is_serviceability_requested_gc(cause) ||
478 cause == GCCause::_metadata_GC_clear_soft_refs ||
479 cause == GCCause::_full_gc_alot ||
480 cause == GCCause::_wb_full_gc ||
481 cause == GCCause::_wb_breakpoint ||
482 cause == GCCause::_scavenge_alot,
483 "only requested GCs here");
484
485 if (is_explicit_gc(cause)) {
486 if (!DisableExplicitGC) {
487 handle_requested_gc(cause);
488 }
489 } else {
490 handle_requested_gc(cause);
491 }
492 }
493
494 void ShenandoahControlThread::handle_requested_gc(GCCause::Cause cause) {
495 // Make sure we have at least one complete GC cycle before unblocking
496 // from the explicit GC request.
497 //
498 // This is especially important for weak references cleanup and/or native
499 // resources (e.g. DirectByteBuffers) machinery: when explicit GC request
500 // comes very late in the already running cycle, it would miss lots of new
501 // opportunities for cleanup that were made available before the caller
502 // requested the GC.
503
504 MonitorLocker ml(&_gc_waiters_lock);
505 size_t current_gc_id = get_gc_id();
506 size_t required_gc_id = current_gc_id + 1;
507 while (current_gc_id < required_gc_id) {
508 _gc_requested.set();
509 _requested_gc_cause = cause;
510
511 if (cause != GCCause::_wb_breakpoint) {
512 ml.wait();
513 }
514 current_gc_id = get_gc_id();
515 }
516 }
517
518 void ShenandoahControlThread::handle_alloc_failure(ShenandoahAllocRequest& req) {
519 ShenandoahHeap* heap = ShenandoahHeap::heap();
520
521 assert(current()->is_Java_thread(), "expect Java thread here");
522
523 if (try_set_alloc_failure_gc()) {
524 // Only report the first allocation failure
525 log_info(gc)("Failed to allocate %s, " SIZE_FORMAT "%s",
526 req.type_string(),
527 byte_size_in_proper_unit(req.size() * HeapWordSize), proper_unit_for_byte_size(req.size() * HeapWordSize));
528
529 // Now that alloc failure GC is scheduled, we can abort everything else
530 heap->cancel_gc(GCCause::_allocation_failure);
574 _do_counters_update.unset();
575 ShenandoahHeap::heap()->monitoring_support()->update_counters();
576 }
577 }
578
579 void ShenandoahControlThread::handle_force_counters_update() {
580 if (_force_counters_update.is_set()) {
581 _do_counters_update.unset(); // reset these too, we do update now!
582 ShenandoahHeap::heap()->monitoring_support()->update_counters();
583 }
584 }
585
586 void ShenandoahControlThread::notify_heap_changed() {
587 // This is called from allocation path, and thus should be fast.
588
589 // Update monitoring counters when we took a new region. This amortizes the
590 // update costs on slow path.
591 if (_do_counters_update.is_unset()) {
592 _do_counters_update.set();
593 }
594 // Notify that something had changed.
595 if (_heap_changed.is_unset()) {
596 _heap_changed.set();
597 }
598 }
599
600 void ShenandoahControlThread::pacing_notify_alloc(size_t words) {
601 assert(ShenandoahPacing, "should only call when pacing is enabled");
602 Atomic::add(&_allocs_seen, words, memory_order_relaxed);
603 }
604
605 void ShenandoahControlThread::set_forced_counters_update(bool value) {
606 _force_counters_update.set_cond(value);
607 }
608
609 void ShenandoahControlThread::reset_gc_id() {
610 Atomic::store(&_gc_id, (size_t)0);
611 }
612
613 void ShenandoahControlThread::update_gc_id() {
614 Atomic::inc(&_gc_id);
615 }
616
617 size_t ShenandoahControlThread::get_gc_id() {
622 print_on(tty);
623 }
624
625 void ShenandoahControlThread::print_on(outputStream* st) const {
626 st->print("Shenandoah Concurrent Thread");
627 Thread::print_on(st);
628 st->cr();
629 }
630
631 void ShenandoahControlThread::start() {
632 create_and_start();
633 }
634
635 void ShenandoahControlThread::prepare_for_graceful_shutdown() {
636 _graceful_shutdown.set();
637 }
638
639 bool ShenandoahControlThread::in_graceful_shutdown() {
640 return _graceful_shutdown.is_set();
641 }
|
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
27 #include "gc/shenandoah/shenandoahConcurrentGC.hpp"
28 #include "gc/shenandoah/shenandoahControlThread.hpp"
29 #include "gc/shenandoah/shenandoahDegeneratedGC.hpp"
30 #include "gc/shenandoah/shenandoahFreeSet.hpp"
31 #include "gc/shenandoah/shenandoahFullGC.hpp"
32 #include "gc/shenandoah/shenandoahGeneration.hpp"
33 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
34 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
35 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
36 #include "gc/shenandoah/shenandoahMark.inline.hpp"
37 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
38 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
39 #include "gc/shenandoah/shenandoahOldGC.hpp"
40 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
41 #include "gc/shenandoah/shenandoahUtils.hpp"
42 #include "gc/shenandoah/shenandoahVMOperations.hpp"
43 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
44 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
45 #include "gc/shenandoah/mode/shenandoahMode.hpp"
46 #include "memory/iterator.hpp"
47 #include "memory/metaspaceUtils.hpp"
48 #include "memory/metaspaceStats.hpp"
49 #include "memory/universe.hpp"
50 #include "runtime/atomic.hpp"
51
52 ShenandoahControlThread::ShenandoahControlThread() :
53 ConcurrentGCThread(),
54 _alloc_failure_waiters_lock(Mutex::leaf, "ShenandoahAllocFailureGC_lock", Monitor::_safepoint_check_always, true),
55 _gc_waiters_lock(Mutex::leaf, "ShenandoahRequestedGC_lock", Monitor::_safepoint_check_always, true),
56 _control_lock(Mutex::leaf - 1, "ShenandoahControlGC_lock", Monitor::_safepoint_check_never, true),
57 _periodic_task(this),
58 _requested_gc_cause(GCCause::_no_cause_specified),
59 _requested_generation(GenerationMode::GLOBAL),
60 _degen_point(ShenandoahGC::_degenerated_outside_cycle),
61 _degen_generation(NULL),
62 _allocs_seen(0),
63 _mode(none) {
64
65 reset_gc_id();
66 create_and_start();
67 _periodic_task.enroll();
68 if (ShenandoahPacing) {
69 _periodic_pacer_notify_task.enroll();
70 }
71 }
72
73 ShenandoahControlThread::~ShenandoahControlThread() {
74 // This is here so that super is called.
75 }
76
77 void ShenandoahPeriodicTask::task() {
78 _thread->handle_force_counters_update();
79 _thread->handle_counters_update();
80 }
81
82 void ShenandoahPeriodicPacerNotify::task() {
83 assert(ShenandoahPacing, "Should not be here otherwise");
84 ShenandoahHeap::heap()->pacer()->notify_waiters();
85 }
86
87 void ShenandoahControlThread::run_service() {
88 ShenandoahHeap* heap = ShenandoahHeap::heap();
89
90 GCMode default_mode = concurrent_normal;
91 GenerationMode generation = GLOBAL;
92 GCCause::Cause default_cause = GCCause::_shenandoah_concurrent_gc;
93
94 double last_shrink_time = os::elapsedTime();
95 uint age_period = 0;
96
97 // Shrink period avoids constantly polling regions for shrinking.
98 // Having a period 10x lower than the delay would mean we hit the
99 // shrinking with lag of less than 1/10-th of true delay.
100 // ShenandoahUncommitDelay is in msecs, but shrink_period is in seconds.
101 double shrink_period = (double)ShenandoahUncommitDelay / 1000 / 10;
102
103 ShenandoahCollectorPolicy* policy = heap->shenandoah_policy();
104
105 // Heuristics are notified of allocation failures here and other outcomes
106 // of the cycle. They're also used here to control whether the Nth consecutive
107 // degenerated cycle should be 'promoted' to a full cycle. The decision to
108 // trigger a cycle or not is evaluated on the regulator thread.
109 ShenandoahHeuristics* global_heuristics = heap->global_generation()->heuristics();
110 while (!in_graceful_shutdown() && !should_terminate()) {
111 // Figure out if we have pending requests.
112 bool alloc_failure_pending = _alloc_failure_gc.is_set();
113 bool explicit_gc_requested = _gc_requested.is_set() && is_explicit_gc(_requested_gc_cause);
114 bool implicit_gc_requested = _gc_requested.is_set() && is_implicit_gc(_requested_gc_cause);
115
116 // This control loop iteration have seen this much allocations.
117 size_t allocs_seen = Atomic::xchg(&_allocs_seen, (size_t)0, memory_order_relaxed);
118
119 // Check if we have seen a new target for soft max heap size.
120 bool soft_max_changed = check_soft_max_changed();
121
122 // Choose which GC mode to run in. The block below should select a single mode.
123 set_gc_mode(none);
124 GCCause::Cause cause = GCCause::_last_gc_cause;
125 ShenandoahGC::ShenandoahDegenPoint degen_point = ShenandoahGC::_degenerated_unset;
126
127 if (alloc_failure_pending) {
128 // Allocation failure takes precedence: we have to deal with it first thing
129 log_info(gc)("Trigger: Handle Allocation Failure");
130
131 cause = GCCause::_allocation_failure;
132
133 // Consume the degen point, and seed it with default value
134 degen_point = _degen_point;
135 _degen_point = ShenandoahGC::_degenerated_outside_cycle;
136
137 if (degen_point == ShenandoahGC::_degenerated_outside_cycle) {
138 _degen_generation = heap->mode()->is_generational() ? heap->young_generation() : heap->global_generation();
139 } else {
140 assert(_degen_generation != NULL, "Need to know which generation to resume.");
141 }
142
143 ShenandoahHeuristics* heuristics = _degen_generation->heuristics();
144 generation = _degen_generation->generation_mode();
145 bool old_gen_evacuation_failed = heap->clear_old_evacuation_failure();
146
147 // Do not bother with degenerated cycle if old generation evacuation failed.
148 if (ShenandoahDegeneratedGC && heuristics->should_degenerate_cycle() && !old_gen_evacuation_failed) {
149 heuristics->record_allocation_failure_gc();
150 policy->record_alloc_failure_to_degenerated(degen_point);
151 set_gc_mode(stw_degenerated);
152 } else {
153 heuristics->record_allocation_failure_gc();
154 policy->record_alloc_failure_to_full();
155 generation = GLOBAL;
156 set_gc_mode(stw_full);
157 }
158 } else if (explicit_gc_requested) {
159 generation = GLOBAL;
160 cause = _requested_gc_cause;
161 log_info(gc)("Trigger: Explicit GC request (%s)", GCCause::to_string(cause));
162
163 global_heuristics->record_requested_gc();
164
165 if (ExplicitGCInvokesConcurrent) {
166 policy->record_explicit_to_concurrent();
167 set_gc_mode(default_mode);
168 // Unload and clean up everything
169 heap->set_unload_classes(global_heuristics->can_unload_classes());
170 } else {
171 policy->record_explicit_to_full();
172 set_gc_mode(stw_full);
173 }
174 } else if (implicit_gc_requested) {
175 generation = GLOBAL;
176 cause = _requested_gc_cause;
177 log_info(gc)("Trigger: Implicit GC request (%s)", GCCause::to_string(cause));
178
179 global_heuristics->record_requested_gc();
180
181 if (ShenandoahImplicitGCInvokesConcurrent) {
182 policy->record_implicit_to_concurrent();
183 set_gc_mode(default_mode);
184
185 // Unload and clean up everything
186 heap->set_unload_classes(global_heuristics->can_unload_classes());
187 } else {
188 policy->record_implicit_to_full();
189 set_gc_mode(stw_full);
190 }
191 } else {
192 // We should only be here if the regulator requested a cycle or if
193 // there is an old generation mark in progress.
194 if (_requested_gc_cause == GCCause::_shenandoah_concurrent_gc) {
195 // preemption was requested or this is a regular cycle
196 cause = GCCause::_shenandoah_concurrent_gc;
197 generation = _requested_generation;
198 set_gc_mode(default_mode);
199
200 // Don't start a new old marking if there is one already in progress.
201 if (generation == OLD && heap->is_concurrent_old_mark_in_progress()) {
202 set_gc_mode(marking_old);
203 }
204
205 if (generation == GLOBAL) {
206 heap->set_unload_classes(global_heuristics->should_unload_classes());
207 } else {
208 heap->set_unload_classes(false);
209 }
210 } else if (heap->is_concurrent_old_mark_in_progress() || heap->is_concurrent_prep_for_mixed_evacuation_in_progress()) {
211 // Nobody asked us to do anything, but we have an old-generation mark or old-generation preparation for
212 // mixed evacuation in progress, so resume working on that.
213 cause = GCCause::_shenandoah_concurrent_gc;
214 generation = OLD;
215 set_gc_mode(marking_old);
216 }
217
218 // Don't want to spin in this loop and start a cycle every time, so
219 // clear requested gc cause. This creates a race with callers of the
220 // blocking 'request_gc' method, but there it loops and resets the
221 // '_requested_gc_cause' until a full cycle is completed.
222 _requested_gc_cause = GCCause::_no_gc;
223 }
224
225 // Blow all soft references on this cycle, if handling allocation failure,
226 // either implicit or explicit GC request, or we are requested to do so unconditionally.
227 if (generation == GLOBAL && (alloc_failure_pending || implicit_gc_requested || explicit_gc_requested || ShenandoahAlwaysClearSoftRefs)) {
228 heap->soft_ref_policy()->set_should_clear_all_soft_refs(true);
229 }
230
231 bool gc_requested = (_mode != none);
232 assert (!gc_requested || cause != GCCause::_last_gc_cause, "GC cause should be set");
233
234 if (gc_requested) {
235 // GC is starting, bump the internal ID
236 update_gc_id();
237
238 heap->reset_bytes_allocated_since_gc_start();
239
240 MetaspaceCombinedStats meta_sizes = MetaspaceUtils::get_combined_statistics();
241
242 // If GC was requested, we are sampling the counters even without actual triggers
243 // from allocation machinery. This captures GC phases more accurately.
244 set_forced_counters_update(true);
245
246 // If GC was requested, we better dump freeset data for performance debugging
247 {
248 ShenandoahHeapLocker locker(heap->lock());
249 heap->free_set()->log_status();
250 }
251
252 heap->set_aging_cycle(false);
253 {
254 switch (_mode) {
255 case concurrent_normal: {
256 if ((generation == YOUNG) && (age_period-- == 0)) {
257 heap->set_aging_cycle(true);
258 age_period = ShenandoahAgingCyclePeriod - 1;
259 }
260 service_concurrent_normal_cycle(heap, generation, cause);
261 break;
262 }
263 case stw_degenerated: {
264 if (!service_stw_degenerated_cycle(cause, degen_point)) {
265 // The degenerated GC was upgraded to a Full GC
266 generation = GLOBAL;
267 }
268 break;
269 }
270 case stw_full: {
271 service_stw_full_cycle(cause);
272 break;
273 }
274 case marking_old: {
275 assert(generation == OLD, "Expected old generation here");
276 resume_concurrent_old_cycle(heap->old_generation(), cause);
277 break;
278 }
279 default: {
280 ShouldNotReachHere();
281 }
282 }
283 }
284
285 // If this was the requested GC cycle, notify waiters about it
286 if (explicit_gc_requested || implicit_gc_requested) {
287 notify_gc_waiters();
288 }
289
290 // If this was the allocation failure GC cycle, notify waiters about it
291 if (alloc_failure_pending) {
292 notify_alloc_failure_waiters();
293 }
294
295 // Report current free set state at the end of cycle, whether
296 // it is a normal completion, or the abort.
297 {
298 ShenandoahHeapLocker locker(heap->lock());
299 heap->free_set()->log_status();
300
301 // Notify Universe about new heap usage. This has implications for
302 // global soft refs policy, and we better report it every time heap
303 // usage goes down.
304 Universe::heap()->update_capacity_and_used_at_gc();
305
306 // Signal that we have completed a visit to all live objects.
307 Universe::heap()->record_whole_heap_examined_timestamp();
308 }
309
310 // Disable forced counters update, and update counters one more time
311 // to capture the state at the end of GC session.
312 handle_force_counters_update();
313 set_forced_counters_update(false);
314
315 // Retract forceful part of soft refs policy
316 heap->soft_ref_policy()->set_should_clear_all_soft_refs(false);
317
318 // Clear metaspace oom flag, if current cycle unloaded classes
319 if (heap->unload_classes()) {
320 assert(generation == GLOBAL, "Only unload classes during GLOBAL cycle");
321 global_heuristics->clear_metaspace_oom();
322 }
323
324 // Commit worker statistics to cycle data
325 heap->phase_timings()->flush_par_workers_to_cycle();
326 if (ShenandoahPacing) {
327 heap->pacer()->flush_stats_to_cycle();
328 }
329
330 // Print GC stats for current cycle
331 {
332 LogTarget(Info, gc, stats) lt;
333 if (lt.is_enabled()) {
334 ResourceMark rm;
335 LogStream ls(lt);
336 heap->phase_timings()->print_cycle_on(&ls);
337 if (ShenandoahPacing) {
338 heap->pacer()->print_cycle_on(&ls);
339 }
340 }
341 }
360 double current = os::elapsedTime();
361
362 if (ShenandoahUncommit && (explicit_gc_requested || soft_max_changed || (current - last_shrink_time > shrink_period))) {
363 // Explicit GC tries to uncommit everything down to min capacity.
364 // Soft max change tries to uncommit everything down to target capacity.
365 // Periodic uncommit tries to uncommit suitable regions down to min capacity.
366
367 double shrink_before = (explicit_gc_requested || soft_max_changed) ?
368 current :
369 current - (ShenandoahUncommitDelay / 1000.0);
370
371 size_t shrink_until = soft_max_changed ?
372 heap->soft_max_capacity() :
373 heap->min_capacity();
374
375 service_uncommit(shrink_before, shrink_until);
376 heap->phase_timings()->flush_cycle_to_global();
377 last_shrink_time = current;
378 }
379
380 // Don't wait around if there was an allocation failure - start the next cycle immediately.
381 if (!is_alloc_failure_gc()) {
382 // The timed wait is necessary because this thread has a responsibility to send
383 // 'alloc_words' to the pacer when it does not perform a GC.
384 MonitorLocker lock(&_control_lock, Mutex::_no_safepoint_check_flag);
385 lock.wait(ShenandoahControlIntervalMax);
386 }
387 }
388
389 // Wait for the actual stop(), can't leave run_service() earlier.
390 while (!should_terminate()) {
391 os::naked_short_sleep(ShenandoahControlIntervalMin);
392 }
393 }
394
395 // Young and old concurrent cycles are initiated by the regulator. Implicit
396 // and explicit GC requests are handled by the controller thread and always
397 // run a global cycle (which is concurrent by default, but may be overridden
398 // by command line options). Old cycles always degenerate to a global cycle.
399 // Young cycles are degenerated to complete the young cycle. Young
400 // and old degen may upgrade to Full GC. Full GC may also be
401 // triggered directly by a System.gc() invocation.
402 //
403 //
404 // +-----+ Idle +-----+-----------+---------------------+
405 // | + | | |
406 // | | | | |
407 // | | v | |
408 // | | Bootstrap Old +-- | ------------+ |
409 // | | + | | |
410 // | | | | | |
411 // | v v v v |
412 // | Resume Old <----------+ Young +--> Young Degen |
413 // | + + + |
414 // v | | | |
415 // Global <-+ | | |
416 // + | | |
417 // | v v |
418 // +---> Global Degen +--------------------> Full <----+
419 //
420 void ShenandoahControlThread::service_concurrent_normal_cycle(
421 const ShenandoahHeap* heap, const GenerationMode generation, GCCause::Cause cause) {
422
423 switch (generation) {
424 case YOUNG: {
425 // Run a young cycle. This might or might not, have interrupted an ongoing
426 // concurrent mark in the old generation. We need to think about promotions
427 // in this case. Promoted objects should be above the TAMS in the old regions
428 // they end up in, but we have to be sure we don't promote into any regions
429 // that are in the cset.
430 log_info(gc, ergo)("Start GC cycle (YOUNG)");
431 service_concurrent_cycle(heap->young_generation(), cause, false);
432 heap->young_generation()->log_status();
433 break;
434 }
435 case GLOBAL: {
436 log_info(gc, ergo)("Start GC cycle (GLOBAL)");
437 service_concurrent_cycle(heap->global_generation(), cause, false);
438 heap->global_generation()->log_status();
439 break;
440 }
441 case OLD: {
442 log_info(gc, ergo)("Start GC cycle (OLD)");
443 service_concurrent_old_cycle(heap, cause);
444 heap->old_generation()->log_status();
445 break;
446 }
447 default:
448 ShouldNotReachHere();
449 }
450 }
451
452 void ShenandoahControlThread::service_concurrent_old_cycle(const ShenandoahHeap* heap, GCCause::Cause &cause) {
453 // Configure the young generation's concurrent mark to put objects in
454 // old regions into the concurrent mark queues associated with the old
455 // generation. The young cycle will run as normal except that rather than
456 // ignore old references it will mark and enqueue them in the old concurrent
457 // mark but it will not traverse them.
458 ShenandoahGeneration* old_generation = heap->old_generation();
459 ShenandoahYoungGeneration* young_generation = heap->young_generation();
460
461 assert(!heap->is_concurrent_old_mark_in_progress(), "Old already in progress.");
462 assert(old_generation->task_queues()->is_empty(), "Old mark queues should be empty.");
463
464 young_generation->set_old_gen_task_queues(old_generation->task_queues());
465 young_generation->set_mark_incomplete();
466 old_generation->set_mark_incomplete();
467 service_concurrent_cycle(young_generation, cause, true);
468 if (!heap->cancelled_gc()) {
469 // Reset the degenerated point. Normally this would happen at the top
470 // of the control loop, but here we have just completed a young cycle
471 // which has bootstrapped the old concurrent marking.
472 _degen_point = ShenandoahGC::_degenerated_outside_cycle;
473
474 // TODO: Bit of a hack here to keep the phase timings happy as we transition
475 // to concurrent old marking. We need to revisit this.
476 heap->phase_timings()->flush_par_workers_to_cycle();
477 heap->phase_timings()->flush_cycle_to_global();
478
479 // From here we will 'resume' the old concurrent mark. This will skip reset
480 // and init mark for the concurrent mark. All of that work will have been
481 // done by the bootstrapping young cycle. In order to simplify the debugging
482 // effort, the old cycle will ONLY complete the mark phase. No actual
483 // collection of the old generation is happening here.
484 set_gc_mode(marking_old);
485 resume_concurrent_old_cycle(old_generation, cause);
486 }
487 }
488
489 bool ShenandoahControlThread::check_soft_max_changed() const {
490 ShenandoahHeap* heap = ShenandoahHeap::heap();
491 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
492 size_t old_soft_max = heap->soft_max_capacity();
493 if (new_soft_max != old_soft_max) {
494 new_soft_max = MAX2(heap->min_capacity(), new_soft_max);
495 new_soft_max = MIN2(heap->max_capacity(), new_soft_max);
496 if (new_soft_max != old_soft_max) {
497 log_info(gc)("Soft Max Heap Size: " SIZE_FORMAT "%s -> " SIZE_FORMAT "%s",
498 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
499 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
500 );
501 heap->set_soft_max_capacity(new_soft_max);
502 return true;
503 }
504 }
505 return false;
506 }
507
508 void ShenandoahControlThread::resume_concurrent_old_cycle(ShenandoahGeneration* generation, GCCause::Cause cause) {
509
510 assert(ShenandoahHeap::heap()->is_concurrent_old_mark_in_progress() ||
511 ShenandoahHeap::heap()->is_concurrent_prep_for_mixed_evacuation_in_progress(),
512 "Old mark or mixed-evac prep should be in progress");
513 log_debug(gc)("Resuming old generation with " UINT32_FORMAT " marking tasks queued.", generation->task_queues()->tasks());
514
515 ShenandoahHeap* heap = ShenandoahHeap::heap();
516
517 GCIdMark gc_id_mark;
518 ShenandoahGCSession session(cause, generation);
519
520 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
521 // We can only tolerate being cancelled during concurrent marking or during preparation for mixed
522 // evacuation. This flag here (passed by reference) is used to control precisely where the regulator
523 // is allowed to cancel a GC.
524 ShenandoahOldGC gc(generation, _allow_old_preemption);
525 if (gc.collect(cause)) {
526 // Old collection is complete, the young generation no longer needs this
527 // reference to the old concurrent mark so clean it up.
528 heap->young_generation()->set_old_gen_task_queues(NULL);
529 generation->heuristics()->record_success_concurrent();
530 heap->shenandoah_policy()->record_success_concurrent();
531 }
532
533 if (heap->cancelled_gc()) {
534 // It's possible the gc cycle was cancelled after the last time
535 // the collection checked for cancellation. In which case, the
536 // old gc cycle is still completed, and we have to deal with this
537 // cancellation. We set the degeneration point to be outside
538 // the cycle because if this is an allocation failure, that is
539 // what must be done (there is no degenerated old cycle). If the
540 // cancellation was due to a heuristic wanting to start a young
541 // cycle, then we are not actually going to a degenerated cycle,
542 // so the degenerated point doesn't matter here.
543 check_cancellation_or_degen(ShenandoahGC::_degenerated_outside_cycle);
544 }
545 }
546
547 void ShenandoahControlThread::service_concurrent_cycle(ShenandoahGeneration* generation, GCCause::Cause cause, bool do_old_gc_bootstrap) {
548 // Normal cycle goes via all concurrent phases. If allocation failure (af) happens during
549 // any of the concurrent phases, it first degrades to Degenerated GC and completes GC there.
550 // If second allocation failure happens during Degenerated GC cycle (for example, when GC
551 // tries to evac something and no memory is available), cycle degrades to Full GC.
552 //
553 // There are also a shortcut through the normal cycle: immediate garbage shortcut, when
554 // heuristics says there are no regions to compact, and all the collection comes from immediately
555 // reclaimable regions.
556 //
557 // ................................................................................................
558 //
559 // (immediate garbage shortcut) Concurrent GC
560 // /-------------------------------------------\
561 // | |
562 // | |
563 // | |
564 // | v
565 // [START] ----> Conc Mark ----o----> Conc Evac --o--> Conc Update-Refs ---o----> [END]
566 // | | | ^
567 // | (af) | (af) | (af) |
568 // ..................|....................|.................|..............|.......................
569 // | | | |
570 // | | | | Degenerated GC
571 // v v v |
572 // STW Mark ----------> STW Evac ----> STW Update-Refs ----->o
573 // | | | ^
574 // | (af) | (af) | (af) |
575 // ..................|....................|.................|..............|.......................
576 // | | | |
577 // | v | | Full GC
578 // \------------------->o<----------------/ |
579 // | |
580 // v |
581 // Full GC --------------------------/
582 //
583 ShenandoahHeap* heap = ShenandoahHeap::heap();
584 if (check_cancellation_or_degen(ShenandoahGC::_degenerated_outside_cycle)) return;
585
586 GCIdMark gc_id_mark;
587 ShenandoahGCSession session(cause, generation);
588
589 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
590
591 ShenandoahConcurrentGC gc(generation, do_old_gc_bootstrap);
592 if (gc.collect(cause)) {
593 // Cycle is complete
594 generation->heuristics()->record_success_concurrent();
595 heap->shenandoah_policy()->record_success_concurrent();
596 } else {
597 assert(heap->cancelled_gc(), "Must have been cancelled");
598 check_cancellation_or_degen(gc.degen_point());
599 assert(generation->generation_mode() != OLD, "Old GC takes a different control path");
600 // Concurrent young-gen collection degenerates to young
601 // collection. Same for global collections.
602 _degen_generation = generation;
603 }
604 }
605
606 bool ShenandoahControlThread::check_cancellation_or_degen(ShenandoahGC::ShenandoahDegenPoint point) {
607 ShenandoahHeap* heap = ShenandoahHeap::heap();
608 if (!heap->cancelled_gc()) {
609 return false;
610 }
611
612 if (in_graceful_shutdown()) {
613 return true;
614 }
615
616 assert(_degen_point == ShenandoahGC::_degenerated_outside_cycle,
617 "Should not be set yet: %s", ShenandoahGC::degen_point_to_string(_degen_point));
618
619 if (is_alloc_failure_gc()) {
620 _degen_point = point;
621 return true;
622 }
623
624 if (_preemption_requested.is_set()) {
625 assert(_requested_generation == YOUNG, "Only young GCs may preempt old.");
626 _preemption_requested.unset();
627
628 // Old generation marking is only cancellable during concurrent marking.
629 // Once final mark is complete, the code does not check again for cancellation.
630 // If old generation was cancelled for an allocation failure, we wouldn't
631 // make it to this case. The calling code is responsible for forcing a
632 // cancellation due to allocation failure into a degenerated cycle.
633 _degen_point = point;
634 heap->clear_cancelled_gc(false /* clear oom handler */);
635 return true;
636 }
637
638 fatal("Cancel GC either for alloc failure GC, or gracefully exiting, or to pause old generation marking.");
639 return false;
640 }
641
642 void ShenandoahControlThread::stop_service() {
643 // Nothing to do here.
644 }
645
646 void ShenandoahControlThread::service_stw_full_cycle(GCCause::Cause cause) {
647 ShenandoahHeap* const heap = ShenandoahHeap::heap();
648
649 GCIdMark gc_id_mark;
650 ShenandoahGCSession session(cause, heap->global_generation());
651
652 ShenandoahFullGC gc;
653 gc.collect(cause);
654
655 heap->global_generation()->heuristics()->record_success_full();
656 heap->shenandoah_policy()->record_success_full();
657 }
658
659 bool ShenandoahControlThread::service_stw_degenerated_cycle(GCCause::Cause cause, ShenandoahGC::ShenandoahDegenPoint point) {
660 assert (point != ShenandoahGC::_degenerated_unset, "Degenerated point should be set");
661 ShenandoahHeap* const heap = ShenandoahHeap::heap();
662
663 GCIdMark gc_id_mark;
664 ShenandoahGCSession session(cause, _degen_generation);
665
666 ShenandoahDegenGC gc(point, _degen_generation);
667
668 // Just in case degenerated cycle preempted old-gen marking, clear the old-gen task queues.
669 heap->young_generation()->set_old_gen_task_queues(NULL);
670
671 gc.collect(cause);
672
673 assert(heap->young_generation()->task_queues()->is_empty(), "Unexpected young generation marking tasks");
674 assert(heap->old_generation()->task_queues()->is_empty(), "Unexpected old generation marking tasks");
675 assert(heap->global_generation()->task_queues()->is_empty(), "Unexpected global generation marking tasks");
676
677 _degen_generation->heuristics()->record_success_degenerated();
678 heap->shenandoah_policy()->record_success_degenerated();
679 return !gc.upgraded_to_full();
680 }
681
682 void ShenandoahControlThread::service_uncommit(double shrink_before, size_t shrink_until) {
683 ShenandoahHeap* heap = ShenandoahHeap::heap();
684
685 // Determine if there is work to do. This avoids taking heap lock if there is
686 // no work available, avoids spamming logs with superfluous logging messages,
687 // and minimises the amount of work while locks are taken.
688
689 if (heap->committed() <= shrink_until) return;
690
691 bool has_work = false;
692 for (size_t i = 0; i < heap->num_regions(); i++) {
693 ShenandoahHeapRegion *r = heap->get_region(i);
694 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
695 has_work = true;
696 break;
697 }
698 }
699
700 if (has_work) {
701 heap->entry_uncommit(shrink_before, shrink_until);
702 }
703 }
704
705 bool ShenandoahControlThread::is_explicit_gc(GCCause::Cause cause) const {
706 return GCCause::is_user_requested_gc(cause) ||
707 GCCause::is_serviceability_requested_gc(cause);
708 }
709
710 bool ShenandoahControlThread::is_implicit_gc(GCCause::Cause cause) const {
711 return !is_explicit_gc(cause) && cause != GCCause::_shenandoah_concurrent_gc;
712 }
713
714 void ShenandoahControlThread::request_gc(GCCause::Cause cause) {
715 assert(GCCause::is_user_requested_gc(cause) ||
716 GCCause::is_serviceability_requested_gc(cause) ||
717 cause == GCCause::_metadata_GC_clear_soft_refs ||
718 cause == GCCause::_full_gc_alot ||
719 cause == GCCause::_wb_full_gc ||
720 cause == GCCause::_wb_breakpoint ||
721 cause == GCCause::_scavenge_alot,
722 "only requested GCs here");
723
724 if (is_explicit_gc(cause)) {
725 if (!DisableExplicitGC) {
726 handle_requested_gc(cause);
727 }
728 } else {
729 handle_requested_gc(cause);
730 }
731 }
732
733 bool ShenandoahControlThread::request_concurrent_gc(GenerationMode generation) {
734 if (_preemption_requested.is_set() || _gc_requested.is_set() || ShenandoahHeap::heap()->cancelled_gc()) {
735 // ignore subsequent requests from the heuristics
736 return false;
737 }
738
739 if (_mode == none) {
740 _requested_gc_cause = GCCause::_shenandoah_concurrent_gc;
741 _requested_generation = generation;
742 notify_control_thread();
743 return true;
744 }
745
746 if (preempt_old_marking(generation)) {
747 log_info(gc)("Preempting old generation mark to allow young GC.");
748 _requested_gc_cause = GCCause::_shenandoah_concurrent_gc;
749 _requested_generation = generation;
750 _preemption_requested.set();
751 ShenandoahHeap::heap()->cancel_gc(GCCause::_shenandoah_concurrent_gc);
752 notify_control_thread();
753 return true;
754 }
755
756 return false;
757 }
758
759 void ShenandoahControlThread::notify_control_thread() {
760 MonitorLocker locker(&_control_lock, Mutex::_no_safepoint_check_flag);
761 _control_lock.notify();
762 }
763
764 bool ShenandoahControlThread::preempt_old_marking(GenerationMode generation) {
765 return generation == YOUNG && _allow_old_preemption.try_unset();
766 }
767
768 void ShenandoahControlThread::handle_requested_gc(GCCause::Cause cause) {
769 // Make sure we have at least one complete GC cycle before unblocking
770 // from the explicit GC request.
771 //
772 // This is especially important for weak references cleanup and/or native
773 // resources (e.g. DirectByteBuffers) machinery: when explicit GC request
774 // comes very late in the already running cycle, it would miss lots of new
775 // opportunities for cleanup that were made available before the caller
776 // requested the GC.
777
778 MonitorLocker ml(&_gc_waiters_lock);
779 size_t current_gc_id = get_gc_id();
780 size_t required_gc_id = current_gc_id + 1;
781 while (current_gc_id < required_gc_id) {
782 _gc_requested.set();
783 _requested_gc_cause = cause;
784 notify_control_thread();
785 if (cause != GCCause::_wb_breakpoint) {
786 ml.wait();
787 }
788 current_gc_id = get_gc_id();
789 }
790 }
791
792 void ShenandoahControlThread::handle_alloc_failure(ShenandoahAllocRequest& req) {
793 ShenandoahHeap* heap = ShenandoahHeap::heap();
794
795 assert(current()->is_Java_thread(), "expect Java thread here");
796
797 if (try_set_alloc_failure_gc()) {
798 // Only report the first allocation failure
799 log_info(gc)("Failed to allocate %s, " SIZE_FORMAT "%s",
800 req.type_string(),
801 byte_size_in_proper_unit(req.size() * HeapWordSize), proper_unit_for_byte_size(req.size() * HeapWordSize));
802
803 // Now that alloc failure GC is scheduled, we can abort everything else
804 heap->cancel_gc(GCCause::_allocation_failure);
848 _do_counters_update.unset();
849 ShenandoahHeap::heap()->monitoring_support()->update_counters();
850 }
851 }
852
853 void ShenandoahControlThread::handle_force_counters_update() {
854 if (_force_counters_update.is_set()) {
855 _do_counters_update.unset(); // reset these too, we do update now!
856 ShenandoahHeap::heap()->monitoring_support()->update_counters();
857 }
858 }
859
860 void ShenandoahControlThread::notify_heap_changed() {
861 // This is called from allocation path, and thus should be fast.
862
863 // Update monitoring counters when we took a new region. This amortizes the
864 // update costs on slow path.
865 if (_do_counters_update.is_unset()) {
866 _do_counters_update.set();
867 }
868 }
869
870 void ShenandoahControlThread::pacing_notify_alloc(size_t words) {
871 assert(ShenandoahPacing, "should only call when pacing is enabled");
872 Atomic::add(&_allocs_seen, words, memory_order_relaxed);
873 }
874
875 void ShenandoahControlThread::set_forced_counters_update(bool value) {
876 _force_counters_update.set_cond(value);
877 }
878
879 void ShenandoahControlThread::reset_gc_id() {
880 Atomic::store(&_gc_id, (size_t)0);
881 }
882
883 void ShenandoahControlThread::update_gc_id() {
884 Atomic::inc(&_gc_id);
885 }
886
887 size_t ShenandoahControlThread::get_gc_id() {
892 print_on(tty);
893 }
894
895 void ShenandoahControlThread::print_on(outputStream* st) const {
896 st->print("Shenandoah Concurrent Thread");
897 Thread::print_on(st);
898 st->cr();
899 }
900
901 void ShenandoahControlThread::start() {
902 create_and_start();
903 }
904
905 void ShenandoahControlThread::prepare_for_graceful_shutdown() {
906 _graceful_shutdown.set();
907 }
908
909 bool ShenandoahControlThread::in_graceful_shutdown() {
910 return _graceful_shutdown.is_set();
911 }
912
913 const char* ShenandoahControlThread::gc_mode_name(ShenandoahControlThread::GCMode mode) {
914 switch (mode) {
915 case none: return "idle";
916 case concurrent_normal: return "normal";
917 case stw_degenerated: return "degenerated";
918 case stw_full: return "full";
919 case marking_old: return "old mark";
920 default: return "unknown";
921 }
922 }
923
924 void ShenandoahControlThread::set_gc_mode(ShenandoahControlThread::GCMode new_mode) {
925 if (_mode != new_mode) {
926 log_info(gc)("Transition from: %s to: %s", gc_mode_name(_mode), gc_mode_name(new_mode));
927 _mode = new_mode;
928 }
929 }
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